The results of the meta-analyses in a rapid evidence assessment relating to persistent/prolific offenders [1] were interpreted as finding the following:

Positive evidence that structured therapeutic community interventions for drug users in prisons and drug treatments (including drug courts) in the community produced a greater reduction in offending behaviour than standard treatment.

Potential evidence that cognitive skills courses in prison and the community produced a greater reduction in offending behaviour than standard treatment.

Insufficient evidence about the effects of other types of interventions (e.g. case management and differing levels of supervision practice in the probation service) on offending behaviour.

Insufficient evidence to conduct a statistical analysis of the evidence of the duration of treatment effect.

The majority of the studies (85%) were rated as having either moderate or low methodological quality.

A systematic review [2] asked the question: do criminal justice/ correctional services interventions for juvenile offenders lead to a reduction in offending (including frequency and severity of offending)? It drew the following conclusions:

The ‘personal skills training plus’ interventions reduce the risk of re-offending in first time / non-serious offenders when compared to a standard diversion intervention comprising of warning and monitoring.

However, the studies with the most positive results were US-based and based on small numbers of studies. Further research is therefore needed, because the results may not be transferable directly to the UK.